It is required to know which type of light source is used in a lighting system in particular applications. For example, when lamps have to be replaced with more energy-friendly lamps, one would like to replace existing light source with light sources that have about the same light emission characteristics and, thus, knowledge about the currently installed light sources and light emitters is required. In other applications, a lighting system controls the light source such that a specific, predefined, illumination pattern is obtained in the illuminated environment. A controller of such a lighting system has to have some knowledge about the characteristics of the light source such that it is able to predict how the light source must be controlled to obtain the specific predefined illumination pattern.
In a first solution the characteristics of the installed light sources are manually provided to the controller of the lighting system. Every moment in time that a light source is replaced, new light source characteristics must be provided to the controller. In a second solution, a light source is controlled in the operational mode and an image is taken of the illuminated environment to detect what the influence of the light source is on the environment and, possibly, to derive light source characteristics from the image. Although the second solution may be performed automatically and may even be performed every time that the lighting system is switched on, it has specific disadvantages: reflected light is used to characterize the light sources and, as such, the environment influences the determination of the characteristics of the light source. For example, when the whole environment has a relatively dark color, the light intensity emitted by the light source will be underestimated.
Published patent application WO2008/001259 discloses a method of controlling a lighting system based on a target light distribution. Influence data is obtained for the light sources of the lighting system with a camera. The influence data comprises information in relation to a specific light source of the lighting system and shows how the illuminated environment is influenced by the operation of a specific light source. When the lighting system has to be controlled according to a target light distribution, the influence data is used to estimate how the light sources must be controlled to obtain an illuminated environment according to the target light distribution.
Patent application GB2453163A discloses a system for determining a three-dimensional representation of an object or scene. The system provides one or more light sources and comprises one or more two-dimensional image capture devices. In order to be able to determine the three-dimensional representation of the object or scene, characteristics of the light source must be known. Light reflected by the object or scene, as captured by the image capture devices, is used to estimate the characteristics. As discussed previously, using reflected light does not necessary lead to an accurate estimation of the light source characteristics.